The present invention relates to a method for processing water which contains nitrogen compounds. More specifically, the present invention relates to a treatment method for water which contains nitrogen compounds, wherein water is processed at normal temperature and pressure. Nitrogen compounds are removed by oxidative breakdown into nitrogen gas. At the same time, chemical oxygen demand (COD) is also reduced.
Waste sources of nitrogen compounds include proteins, which are used in livestock feed production industries; nitric acid, which is used in inorganic pigment production; ammonia, nitric acid, sodium nitrate, and sodium nitrite, which are used in surface processing steps in metal products production industries and electronic machinery appliance manufacturing; and the like. When released into water, nitrogen compounds are responsible for overnitrification. If these nitrogen compounds are released as nitrogen oxides into the atmosphere, they are dangerous to health as primary pollutants. Furthermore, nitrogen oxides participate in a photochemical reaction and become one of the components of smog, a secondary combined pollution phenomenon. As a result, water which contains nitrogen compounds must be processed for denitrification. The dispersal of unprocessed nitrogen compounds into the atmosphere during these processing steps must be prevented.
Waste water which contains nitrogen compounds can also contain organic compounds other than nitrogen compounds. Furthermore, the nitrogen compound itself can be organic or can be oxygen consuming. As a result, the chemical oxygen demand (COD) of water containing nitrogen compounds can be great. In these cases, as nitrogen compounds are broken down, there is also a need to reduce the COD.
Methods such as the activated carbon adsorption method and biological processing methods are well-known as conventional processing methods for nitrogen compounds in waste water. However, when using the activated carbon adsorption method, it is necessary to reactivate the activated carbon when adsorption equilibrium is reached. With reactivation, a highly concentrated nitrogen compound-containing reactivation waste solution is generated. The need for further processing of this waste is an additional problem.
When water containing nitrogen is biologically processed, the breakdown time required is long because the reaction time is relatively slow. A large-volume biological reaction container becomes necessary, and there is an additional problem of a large amount of excess sludge being generated.
In Japanese Laid Open Patent Number 7-100466, a method is proposed wherein waste water containing ammonia is processed by electrolysis in the presence of chloride ions, at a pH between 8 and 12. The ammonium ion and COD components in the water are efficiently degraded and removed. However, this method generates hypochlorite ions as a by-product, which remain in the processed water and must be removed by further processing.
The present inventors have proposed a method for treating waste water which contains an alkanolamine. In this method, an oxidant is added to waste water which contains an alkanolamine. The alkanolamine is oxidized and broken down in the presence of a metal catalyst and heat. By this method, monoethanolamine and the like can be efficiently oxidized and broken down. However, it is desirable to improve this method by eliminating the need for added oxidants or the need to heat to temperatures greater than 100.degree. C.